Today's servers utilize low frequency (e.g. sub-millimeter wave) high speed interconnects for rack-to-rack and blade-to-blade communication. This Process on Record (POR) electrical fabric provide limited data rate v. distance unless substantial equalization is used. An alternative solution consists of using an optical interconnect fabric that uses optical technologies, such as silicon photonics, and various semiconductor technologies along with optical fibers. This alternative solution provides an extremely high data rate over long distances. For medium distance communication within a server farm, the overhead power associated with the optical fabric is excessive, whereas the required error correction on traditional electrical fabric creates substantial latency issues (e.g., hundreds of nanoseconds). This makes both existing technologies (traditional electrical and optical) suboptimal for emerging Rack Scale Architecture RSA servers including high performance computing platforms where transmission distances typically range from 2 to 5 meters.
There are many interconnects within server and high performance computing (HPC) architectures today. These interconnects include within blade interconnects, within rack interconnects, and rack-to-rack or rack-to-switch interconnects. In today's architectures, short interconnects (for example, within rack interconnects and some rack-to-rack interconnects) are often achieved with electrical cables such as Ethernet cables, co-axial cables, or twin-axial cables, depending on the required data rate. For longer distances, an alternative solution consists of using an optical interconnect fabric that utilizes silicon photonics and various semiconductor technologies along with optical fibers. This alternative solution enables extremely high data rates over long distances. However, as new architectures emerge, such as 100 Gigabit Ethernet, traditional electrical connections are becoming prohibitively expensive and power-hungry to support the required data rates and transmission range. For example, to extend the reach of a cable or the given bandwidth on a cable, higher quality cables may need to be used or advanced equalization, modulation, and/or data correction techniques employed, all of which add power and/or latency to the system. For some distances and data rates required in proposed architectures, there is no viable electrical solution today. Optical transmission over fiber is capable of supporting the required data rates and distances, but at a severe power and cost penalty, especially for short to medium distances, such as a few meters.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications and variations thereof will be apparent to those skilled in the art.